Pontiac battery won't charge

2001 Pontiac Bonneville 75k miles. I have had problems before and replaced the spark plugs due to misfirings. My latest issue came after a 600 mile road trip. I went out to start the car and did not get anything, no turn, click, or anything. I thought maybe a light was left on, jumped the car easily and drove around to charge up the battery noting no lights were left on. When I parked and turned off the car I tried to put the keys into accessory mode/ start it. Again, not a sound. I figured it was the alternator and changed it out the next day, charging and jumping the engine. Drove around to charge the engine and parked with the same problem when I tried to restart, nothing.

Side notes while driving the battery gauge would slide between 1/2 - 3/4 of its range every 20 seconds or so. Whenever it slid I could hear some static electricity sound (I believe this would insinuate a problem with the alternator though I had just replaced it).
When I last shut off the the engine I heard the static electricity sound and my dash panel lights lit up randomly lasting about a minute. During this time and after no interior light would turn on, key in the accessory position did nothing and there was no click, crank, or attempt of the engine to turn when I tried to start it.
I did check the fuses before I changed the alternator without finding any problems. I had to use pliers since the removal tool was broken. I believe everything is completely connected and intact as I checked again when I noted all the random dash light on after I shut the car off. They were warm but I presume that would be expected. I do not think I cracked or caused any problem with the pliers but I suppose it may be possible.
Since the car jumped so easily I can’t imagine it being the battery either.

Any thoughts would be greatly appreciated before I have to take the car to the shop.

It could be a dead battery or a bad connection at the battery posts. Are the battery posts and connectors clean? Is the ground connections at the chassis and motor clean? This is where I would start. If you have a meter, you can measure the battery voltage, with the engine off and then with the engine running. It should be at 12.v and then around 14.5 volts.

All battery connections are clean and appropriately grounded. The battery is under my back seat so it is relatively easy to maintain. I don’t think it would be a dead battery because it started up on the first attempt with jumping. I’ve gone back to check any connections to the alternator but have not found any connection issues. I keep hoping it is something stupid I have overlooked to be an easy fix but nothing yet.

I don’t have a meter for the voltage to try that, I don’t think I would get enough use out of buying one either. Thank you for the insight.

If you can get it going, take it to Advance or AutoZone and let them test your charging system for free. They will point you in the right direction.

Get the battery load tested. Get the charging system tested for output. I wouldn’t replace an alternator without first doing some tests.

If a battery won’t take a charge, the battery is shot. Generally its better to put a battery charger on it and if it won’t take a charge, it needs to be replaced. Provided cables and connections are good. Happened to me several times just out of the blue with no warning.

“I don’t have a meter for the voltage to try that, I don’t think I would get enough use out of buying one either”

It would be enormously useful for this problem and a decent one is only $20.

I think Circuitsmith is absolutely correct. Once you get meter and know how to use it you will wonder how you got by so far in life without it. Some of the best money you could spend, on any tool. Even a cheap meter will work ok.

As far the trouble goes, going from what you stated about the problem it sounds to me you have a bad connection somewhere. Possibly in the ignition or ACC circuit. I think the static you are hearing is due to a faulty connection under the dash area and you are hearing sparking across the bad connection. It may be to the ignition switch or possibly at the dash fuse panel. You might find the trouble by looking for signs of burnt terminal connections. When the connection is bad enough it cuts the power off to areas that require it when the ignition is turned ON but since power is being blocked by the bad connection it makes you think the battery is low since nothing happens when you turn the key. A meter will tell you how good the battery condition is when you try to start up the car.

Plain and simple…you say its not your battery but the vehicle starts with a jump on the first time ? What does that tell you ? You are missing something here of simple thought…GET A NEW BATTERY !!

Also trying to charge a dead battery with an alternator can blow the alternator !

The other vehicles battery starts the car buy yours won’t…plain and simple arithmetic.

Think about it !! I have seen batteries that develop a high internal resistance and may read 12.6 volts with no load…turn on parking lamps and drops to zero…How you can say its not your battery but starts with a jump from another vehicle is beyond me… Your battery voltage gauge is jumping because the internal voltage regulator in the alternator is going crazy due to a bad battery. PERIOD.

If you battery was to totally open the voltage from the alternator could sky rocket and damage the computer among other things…EX: pulling a terminal off the battery when the engine is running…A NO NO !

You say you do not want to spend money on a voltmeter all you need is a cheap one from like Harbor Freight for a few $$$. Best thing you can have during this situation…not trying to be mean to you in anyway but you have to understand the facts…have a good day.

BTW most autopart stores will check your batter for free.